Current commercially available electronic displays are dominated by cathode ray tubes ("CRTs") and liquid crystal displays ("LCDs"). LCDs offer advantages in power, size, and safety, while CRTs are well understood and inexpensive to manufacture. Recent advancements in LCD technology have led to the development of large area, high resolution LCDs, initially using a passive matrix scanning technique (i.e., pixels in the display are directly controlled by the address lines), and more recently using active matrix addressing techniques (i.e., the pixels in the display are controlled by addressing transistors associated with each pixel).
Compared with passive matrix LCDs, active matrix LCDs produce higher quality images but require greater capital investments in manufacturing. To manufacture active matrix LCDs, photolithographic masks of the same size as the LCDs and processing equipment suitable for handling the same size substrate are required. In addition, active matrix displays are generally built on glass substrates using either amorphous or polycrystalline thin film transistors ("TFTs") which typically exhibit poor electrical characteristics and low yield. Further, because thin film transistors typically operate at a relatively low speed, the speed of the display is thus limited. Moreover, due to the low device density and low yield associated with thin fim transistors, the resolution of such LCDs is limited.
Besides the above-described TFT LCDS, there has been a great deal of interest in developing silicon backplane LCDs. In contrast to TFT LCDs which use thin film transistor circuits fabricated on a glass substrate as a backplane, silicon backplane LCDs use integrated circuits fabricated on single crystalline silicon substrates as backplanes. Due to the advantages of silicon integrated circuits over TFT circuits, silicon backplane LCDs operate at a higher speed and offer higher resolution and higher yield.
Kaneko, E., "Liquid Crystal TV Displays: Principles and Applications Of Liquid Crystal Displays," KTK Scientific Publishers, 1987, describes a MOS transistor switch matrix addressed liquid crystal TV display. The TV display comprises a MOS transistor-addressed pixel array formed on a single crystalline silicon substrate; the array is integrated with its driving circuit as a hybrid and is connected to the driving circuits by wire bonding. This TV display suffers several significant drawbacks. First, because the yield for the array decreases drastically with increased array size, the size of the display is limited to about one inch by one inch, which is generally too small to be used as a TV or computer display. Second, the driver circuits are not monolithically integrated with the display array, which makes it expensive to fabricate and which also limits the resolution of the display since it is very difficult to interconnect the driver circuits with an array having a large number of pixels using wire bonding. Consequently, the resolution of the described TV display is limited for the purposes described herein. For example, one of the described TV displays has only 240.times.240 pixels formed on an area of 3.6 cm.times.4.8 cm.
Jared et al., "Electrical Addressed Spatial Light Modulator That Uses A dynamic Memory", Optical Letters, (16:22), pp. 1785-1787 (Nov. 15, 1991), describes an electrically addressed spatial light modulator that consists of a silicon VLSI backplane chip and a ferroelectric-liquid-crystal ("FLC") cell. The VLSI chip includes a 64.times.64 array of pixels located at the center of the chip; it is fabricated using a 2 micron, n-well, complementary metal-oxide-semiconductor ("CMOS") process. The 64.times.64 pixel array appears to be monolithically formed with its electronic addressing circuits on the VLSI chip. However, this type of modulator would not be useful for image displays because the array area is too small.
Despite the clear advantages of VLSI backplane LCDs over TFT LCDs in speed and resolution, they are not viewable with the naked eye and are not used commercially for image displays.
Accordingly, it is an object of the present invention to provide a visual display that is small in size but has a high resolution and can be seen by the naked eye;
it is another object of the present invention to provide a visual display that is compatible with VLSI technology, operates at a high speed and has low power consumption;
it is a further object of the present invention to provide a visual display with reduced image aliasing; and
it is still a further object of the present invention to provide a visual display with reduced optical distortion.